class_docstr: Reader for corpora that consist of parenthesis-delineated parse trees,
  like those found in the "combined" section of the Penn Treebank,
  e.g. "(S (NP (DT the) (JJ little) (NN dog)) (VP (VBD barked)))".
code: def _read_block(self, stream):
      if self._detect_blocks == "sexpr":
          return read_sexpr_block(
              stream, comment_char=self._comment_char
          )
      elif self._detect_blocks == "blankline":
          return read_blankline_block(stream)
      elif self._detect_blocks == "unindented_paren":
          # Tokens start with unindented left parens.
          toks = read_regexp_block(stream, start_re=r"^\(")
          # Strip any comments out of the tokens.
          if self._comment_char:
              toks = [
                  re.sub(
                      "(?m)^%s.*" % re.escape(self._comment_char),
                      "",
                      tok,
                  )
                  for tok in toks
              ]
          return toks
      else:
          assert 0, "bad block type"
  
imports: import sys
  from nltk.corpus.reader.api import *
  from nltk.corpus.reader.util import *
  from nltk.tag import map_tag
  from nltk.tree import Tree
label_desc: Use image node_id 2 for calling the BracketParseCorpusReader obj's underlying member method code with example usage: obj._read_block(stream) and returns: read_sexpr_block, read_blankline_block, toks